The Applicant notes that laser beams with a non-Gaussian intensity profile can be advantageous in the fields of laser materials processing, medicine, and others. Methods of producing such non-Gaussian beams can be divided into two classes, namely extra-cavity [1-2] and intra-cavity [3-4] beam shaping.
In laser-based applications such as additive manufacturing, laser surface engineering, biology, and medicine involving time evolving processes, it may be important to get a controllable intensity shape of laser beam with low response time [5-6].
Recently, an intra-cavity Spatial Light Modulator (SLM) was successfully implemented to produce a controllable beam shaping inside a laser cavity [7]. However, this technique has some limitations with scaling up of output power due to low damage thresholds of SLMs.
Additionally, the SLM has a relatively long response time that limits implementation with high speed applications. Moreover, variation of reflectivity for different grey scale levels (phase) of intra cavity SLM creates additional problems for controllable intra-cavity beam shaping [8].
Another option for intra-cavity beam shaping is to manipulate a gain profile in a laser crystal to perform beam shaping to control the weighting of the desired mode in the output beam. This technique allows simultaneous and controllable variation of both the output power and the transverse intensity distribution of laser beam [9]. A disadvantage of this technique is the limitation for the spatial shape intensities of output beam by laser cavity geometry.
The Applicant desires a controllable laser amplifier which can also perform beam shaping. The Applicant believes that such a laser amplifier would be advantageous if it had high-power capabilities and tolerance to incoherent laser beams.